Fast and slow components of interstadial warming in the North Atlantic during the last glacial

Vasiliki Margari,Joan O Grimalt,Emilie Capron,Belen Martrat,Rachael H Rhodes,David A Hodell,Luke C Skinner,Laurie Menviel,Maryline J Mleneck-Vautravers,Polychronis C Tzedakis,Mohamed M Ezat

doi:10.1038/s43247-020-0006-x

Abstract

The abrupt nature of warming events recorded in Greenland ice-cores during the last glacial has generated much debate over their underlying mechanisms. Here, we present joint marine and terrestrial analyses from the Portuguese Margin, showing a succession of cold stadials and warm interstadials over the interval 35–57 ka. Heinrich stadials 4 and 5 contain considerable structure, with a short transitional phase leading to an interval of maximum cooling and aridity, followed by slowly increasing sea-surface temperatures and moisture availability. A climate model experiment reproduces the changes in western Iberia during the final part of Heinrich stadial 4 as a result of the gradual recovery of the Atlantic meridional overturning circulation. What emerges is that Greenland ice-core records do not provide a unique template for warming events, which involved the operation of both fast and slow components of the coupled atmosphere–ocean–sea-ice system, producing adjustments over a range of timescales.

Highlights

The abrupt nature of warming events recorded in Greenland ice-cores during the last glacial has generated much debate over their underlying mechanisms
A distinction has been made between a Heinrich event (HE; the iceberg discharge through Hudson Strait), a Heinrich layer (HL; the physical manifestation of a HE in a marine sediment core) and a Heinrich stadial (HS; the cold period that contains the HE), underlining the fact that HEs are shorter in duration than the HS in which they occur[7,8]
The similarity in the trajectory of changes following the maximum HS cooling between our data and modelling results suggests that a multi-centennial Atlantic meridional overturning circulation (AMOC) recovery and associated increased oceanic heat transport to the North Atlantic led to a gradual sea-surface temperature (SST) increase and a shift to wetter conditions over western Iberia

Summary

Introduction

The abrupt nature of warming events recorded in Greenland ice-cores during the last glacial has generated much debate over their underlying mechanisms. During Marine Isotopic Stage 3 (MIS 3; 59.5–24 thousand years ago [ka]), multiple high-amplitude air–temperature fluctuations (Dansgaard-Oeschger [DO] stadials and interstadials) have been recognized in Greenland ice-cores and linked to sea-surface temperature (SST) variations and intermittent iceberg discharges in the North Atlantic[1,2]. The structure of this variability in Greenland is characterized by a rapid decadal-scale warming at the onset of an interstadial, a gradual cooling within the interstadial and an abrupt centennialscale cooling leading to stadial conditions[3]. The results reveal diverse patterns and rates of warming, depending on location and underlying processes

Methods

Results

Conclusion